Wood-framed construction often involves supporting beams or joists at their ends by framing the beams or joists into the side of a supporting member such as another beam, girder or ledger, for example. This is in contrast to, for example, situations where the beams or joists are rested on top of a supporting beam or girder. Where joists are framed into the side of a supporting member, hanger brackets, or joist hangers, are commonly used to support the joist off of the supporting member.
For purposes of stability, during construction and throughout the life of a structure, proper construction often provides for bracing the ends of a joist against lateral movement or tipping. Accordingly, designers and product suppliers often specify or recommend that a joist hanger be installed to fit tightly against the sides of the joist at the support location. In some circumstances full depth hangers may be specified such that the joist is supported for its full depth at the support location or at least at the top and bottom of the joist. In other circumstances, minimum ratios of hanger height to joist depth may be specified such that sufficient bracing is provided.
In the case of I-shaped joists, joist hangers may not fit tightly against the web of the joist. In these cases, designers and product suppliers may specify or recommend full depth-type hangers such that the top flange and bottom flange of the joists are prevented from moving laterally relative to one another and relative to the supporting beam. Alternatively, where a full depth hanger is not provided or desired, designers and product suppliers may specify or recommend that web stiffeners be provided to fill the gap between the web of the joist and the side of the hanger providing lateral support to the web. In addition, designers and suppliers may recommend that a minimum ratio of hanger height to joist depth also be maintained.
In still other circumstances, joists may be prone to web buckling due to one or a combination of factors including the slenderness ratio of the web (i.e., thickness/height), loading, or other factors. For overly slender or heavily loaded webs, designers or product suppliers may specify or recommend the use of web stiffeners for sandwiching the web and filling the gap between the web and the sides of the hanger thereby providing lateral support to the web. The web stiffeners in this circumstance may be required even where a full depth-type hanger is provided.
Web stiffeners can be cumbersome and add additional steps to the installation process. Pairs of stiffeners may need to be cut to length and height and suitable thicknesses may need to be provided to properly match the gap between the web and the side of the hanger. Once acquired and cut to length and height, these additional elements may need to be installed against the web of the joist at each end of the joist adding more elements to the connections. Commonly, a bay of a floor or roof framing plan may include a large array of joists and these additional steps can increase the time and cost of constructing the respective floor or roof.